The demand for increased storage capacity in memory or rigid disks and the trend towards miniaturization of memory or rigid disks (e.g., due to the requirement for smaller hard drives in computer equipment) continues to emphasize the importance of the memory or rigid disk manufacturing process, including the planarization or polishing of such disks for ensuring maximal performance. While there exist several chemical-mechanical polishing (CMP) compositions and methods for use in conjunction with semiconductor device manufacture, few conventional CMP methods or commercially available CMP compositions are well-suited for the planarization or polishing of memory or rigid disks.
The term “memory or rigid disk” refers to any magnetic disk, hard disk, rigid disk, or memory disk for retaining information in electromagnetic form. The memory or rigid disk typically has a surface that comprises nickel-phosphorus, but the memory or rigid disk surface can comprise any other suitable material. The planarity of the memory or rigid disks must be improved, as the distance between the recording head of a disk drive and the surface of the memory or rigid disk has decreased with improvements in recording density that demand a lower flying height of the magnetic head with respect to the memory or rigid disk. In order to permit a lower flying height of the magnetic head, improvements to the surface finish of the memory or rigid disk are required.
Surface characteristics of memory or rigid disks affecting the flying height of the magnetic head include waviness, microwaviness, and surface roughness. Waviness or warp is a gross deviation from flatness over the entire disk surface. An intermediate form of surface deviation, herein referred to as microwaviness, may exist. Mircowaviness is a waviness of a disk surface for a range of wavelengths that are on the order of the length of the transducing head. Using current technology, these wavelengths are approximately in the range of 10 to 5000 microns. For low flying head heights, microwaviness can create an airbearing resonance, thereby causing excessive head to disk spacing modulation. The spacing modulation resulting from microwaviness can cause poor overwriting of data on the disk surface, and in some cases can even cause collision of the head with the disk surface with resulting damage to the disk surface and/or the recording head.
Surface roughness is a surface characteristic at yet smaller wavelengths. Surface roughness is a high frequency, short wavelength component of a measured surface which affects performance of memory or rigid disks insofar as it limits the decrease in the gap between the disk surface and the recording head of a disk drive that is practically achievable. Generally, polishing compositions for memory or rigid disks comprise abrasives to increase the removal rates of the substrate. High removal rates also are achieved by an increase in downward force of the polishing pad to the substrate. However, an increase in the downward force leads to abrasive particles becoming embedded into the substrate surface, which negatively impacts surface roughness.
During the polishing of a memory or rigid disk, typically the edges of the disk receive a higher pressure from the polishing tool than the remaining surface of the disk, which leads to the formation of a curved, or rounded, contour at the edges of the disk. The rounded edge areas are known in the art as edge roll-off, rub-off, or dub-off. Such rounded areas on a disk are unsuitable for recording.
A need remains for polishing compositions and methods for planarizing or polishing memory or rigid disks which minimize microwaviness and edge roll-off, without sacrificing the removal rate or surface roughness. The invention provides such polishing compositions and methods. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.